1. Chapter 3 An Introduction to Organic Reactions and Their Mechanism
Acids and Bases

2. 3.7 Inductive Effect
An inductive effect is an electronic effect due to the polarization of σ bonds within a molecule or ion.
In a carbocation, the positive C attracts the electrons in the σ bonds towards itself and away from the atom at the other end of the s bond.
Electrons in C-C bonds are more readily polarized than those in a C-H bond.
Therefore, alkyl groups are better at stabilizing C+ than H atoms.

3. Inductive Effect electron drawing Electron releasing
Inductive effects weaken as the distance from the substituent increases

4. 3.8 Energy Changes Energy is defined as the ability to do work
Kinetic energy and potential energy
Kinetic energy: energy of motion
E = ½ mv2
Potential energy: stored energy

5. Potential Energy

6. Energy Changes
Chemical energy is potential energy (aka relative potential energy)
Attractive and repulsive forces exist between different pieces of the molecules
The more potential energy an object has, the less stable it is

7. 3.8 Potential energy and covalent bond
The state of greatest potential energy is the state of free atoms
Forming a chemical bond is always accompanied by the lowering of potential energy of atoms

8. 3.8 Potential energy and covalent bond

9. Potential energy
Enthalpies or heat contents, H: relative potential energy or (heat) of molecules
ΔHo = change in potential energy between reactants and products
+ ΔHo = endothermic
stronger bonds are formed in the product
- ΔHo = exothermic
Weaker bonds are formed in the product

10. 3.9 The Relationship between the Equilibrium Constant and the Standard Free-Energy Change, ΔGo
ΔGo = -R T ln Keq
R = J/Kmol
- ΔGo = formation of product is favored
Spontaneous
+ ΔGo = formation of product is unfavored
nonspontaneous
ΔGo = ΔHo - T ΔSo

11. Entropy Entropy (S) – measure of disorder or randomness
Randomness increase -> S increases
Sgas> Sion >Smolecule>Ssolid
Ssolid = 0
E.gH2O(s)  H2O (l) S = +
H2O (l)  H2O (g) S = +
H2O (g)  H2O (l) S = -
2nd law of thermodynamic: the entropy of the universe is always increasing

12. Example
State whether you would expect the entropy change ΔSo , to be positive, negative or approximate zero for each of the following reactions. (Assume the reactions take place in the gas phase)
A + B  C
A + B  C + D
A  B +C

13. Example

14. 3.10 The Acidity of Carboxylic acid

15. The Acidity of Carboxylic acids

16. The Acidity of Carboxylic acids

17. 3.10A The effect of Delocalization
Resonance stabilization

18. The Inductive Effect Inductive electron withdrawing effect
Carboxylate ion has two oxygen atoms who combined electronegativity stabilizes the charge more than an alkoxide ion
Lower energy barrier in forming carboxylate ion than alkoxide
Acetic acid is more acidic than ethanol

19. Electrostatic map

20. Inductive effects on Other groups
Substituent effect: the acid-strengthening effect of other electron-attracting groups
Dispersal of charge always makes a species more stable
Any factor that stabilizes the conjugate base of an acid increases the strength of the acid

21. Inductive effects on Other groups